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MS&AD Insurance Group (Aioi Nissay Dowa, Mitsui Sumitomo Insurance, Mitsui Direct) data breach

Was I affected?

MS&AD Insurance Group (Aioi Nissay Dowa, Mitsui Sumitomo Insurance, Mitsui Direct) confirmed a breach involving up to 720,000 records (duplicates possible), exposing names, addresses, phone numbers and email addresses. You may be affected if you hold a policy with Aioi Nissay Dowa, Mitsui Sumitomo Insurance or Mitsui Sumitomo Aioi Life and used their policyholder websites, or if you have or requested a quote for Mitsui Direct car insurance.

MS&AD Insurance Group (Aioi Nissay Dowa, Mitsui Sumitomo Insurance, Mitsui Direct) breach facts
AnnouncedNov 6, 2026
When it happenedDetected November 2, 2026 (Mitsui Direct: November 4, 2026)
CountryJapan
Records exposed (may include duplicates)720,000
Data exposedNames, Addresses, Phone numbers, Email addresses, Dates of birth, Payment card numbers, Bank or financial details and Other details
StatusConfirmed by the company or a regulator filing

What happened

Four insurers in Japan's MS&AD group said on November 6, 2026 that customer data leaked after unauthorized access, about 720,000 records in total. Attackers got into the policyholder web pages of Aioi Nissay Dowa Insurance (about 444,000 records), Mitsui Sumitomo Insurance (about 37,000) and Mitsui Sumitomo Aioi Life (about 5,300), exposing policy numbers, names, addresses, phone numbers and email addresses; at Aioi Nissay Dowa a few records also held the last four card digits or partial bank account numbers. Mitsui Direct General Insurance was breached separately in a different way, leaking about 234,000 records of car insurance customers and quote requesters, including vehicle and contract details. The companies say no misuse has been confirmed so far.

What should I do?

  1. Be wary of calls, emails or texts that quote your policy number or car details and ask you to pay, renew or confirm information; contact your insurer through its official website or the number on your policy.
  2. Change your password for the insurer's policyholder site when it reopens, and anywhere else you reused it.
  3. Check your card and bank statements for charges or debits you don't recognize, especially if you pay Aioi Nissay Dowa premiums by card or account transfer.
  4. Don't open links in unexpected messages about claims or refunds; insurers rarely ask for card or bank details by email or text.
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